Interpretive Summary: Few research models exist that permit bacterial infections to be assessed within the reproductive tract of cattle; a major problem associated with fertility and reduced reproductive performance. The objectives of this study were to characterize the light-emitting properties of an engineered Escherichia coli (E. coli-Xen14) within the bovine reproductive tract, in a laboratory environment, as a model for detecting bacterial presence. Our results indicated that E. coli-Xen14 remained stable with respect to the proportions of light emitting bacteria present, however in the presence of a selective antibiotic, photonic (light) activity of the bacteria was descreased, however we were successful in being able to image bacterial presence through the bovine reproductive tract. The ability to detect light emitted from transformed E. coli bacteria through various segments of the reproductive tract demonstrated the feasibility of monitoring the presence of bacteria in the bovine reproductive tract in the laboratory, and may lead to detection systems for the living animal in the future.

Technical Abstract:
The objectives of this study were to (1) characterize the photonic properties of Escherichia coli-Xen14 and (2) conduct photonic imaging of E. coli-Xen14 within bovine reproductive tract segments (RTS) ex vivo (Bos indicus). E. coli-Xen14 was grown for 24 h in Luria Bertani medium (LB), with or without kanamycin (KAN). Every 24 h, for an 8-d interval, inoculums were imaged and photonic emissions (PE) collected. Inoculums were subcultured and plated daily to determine the colony forming units (CFU) and ratio of photon emitters to nonemitters. In the second objective, abattoir-derived bovine reproductive tracts (n = 9) were separated into posterior and anterior vagina, cervix, uterine body, and uterine horns. Two concentrations (3.2 × 108 and 3.2 × 106 CFU/200 ?L for relative [High] and [Low], respectively) of E. coli-Xen14 were placed in translucent tubes for detection of PE through RTS. The CFU did not differ (P = 0.31) over time with or without KAN presence; they remained stable with 99.93% and 99.98% photon emitters, respectively. However, PE were lower (P < 0.0001) in cultures containing KAN than in those containing no KAN (629.8 ± 117.7 vs. 3012.0 ± 423.5 relative lights units per second [RLU/sec], respectively). On average, the percentage of PE between RTS, for both concentrations, was higher (P < 0.05) in the uterine body. In summary, E. coli-Xen14 remained stable with respect to the proportions of photon emitters with or without KAN (used to selectively culture E. coli-Xen14). However, KAN presence suppressed photonic activity. The ability to detect PE through various segments of the reproductive tract demonstrated the feasibility of monitoring the presence of E. coli-Xen14 in the bovine reproductive tract ex vivo.